In the course of manufacturing printed circuit boards, for example the outer boards of multi-layer printed circuit boards, it is necessary to bring respectively one printed circuit board, which is provided with a defined arrangement of holes, and a film representing a circuit (in manufacturing processes of photo lithography), screen frame (in manufacturing processes of serigraphy) or a different pattern carrier into a very defined relative position in order to place the pattern of the pattern carrier exactly over the hole pattern of the printed circuit board to be produced. For a long time a support supporting a plurality of parallel centering pins has been used for this purpose and the printed circuit boards and films were equipped with a number of centering holes whose arrangement coincided with the arrangement of the centering pins. The mutual orientation required for photo lithography or serigraphy was achieved by placing the centering holes of a printed circuit board and a film on the pins.
This production process no longer satisfies the requirements for accuracy. The reason for this are the unavoidable processing tolerances, in particular of the printed circuit boards. In the process, the tolerances which must be accepted in the course of drilling the centering holes are added to the tolerances in the layer thickness occurring in the course of galvanic coating of the bore hole walls. Because of the mentioned tolerances, the centering pins must have a correspondingly smaller cross section than the centering holes, with the result that many printed circuit boards are only loosely seated on the pins so that during exposure or printing the circuit image of the film or the screen frame is superimposed with a relative displacement on the hole pattern of the printed circuit boards.
The errors created in this manner are increased when the film or other pattern carriers are also seated with play or in a deformed way on the centering pins.
Devices are known from German Utility Model G 88 11 765.0 wherein the centering pins are axially movable and taper conically towards their free ends. Following application of the galvanized printed circuit board, the centering pins are pushed through the centering holes, which are narrowed because of the galvanizing process, with the aid of a pressure medium and then fixed in place. However, because of bores which were displaced because of production tolerances, this will result in deformations of the printed circuit board or even damage to the centering holes, which leads to unacceptable alignment errors.
Since centering of the printed circuit boards and the pattern carriers on pins suffered from inaccuracies which appeared to be unavoidable, optical devices have been developed lately which automatically bring the centering holes in the boards and centering dots on the film to coincidence by moving the boards in relation to the film. However, such devices are extraordinarily expensive in comparison with the pin frame, and the accuracy they can achieve is also limited by the production tolerances of the centering holes in the printed circuit boards.